The color of a light source, also referred to as the chromaticity in the literature, is generally determined using a standardized chromaticity diagram. This standardized chromaticity diagram is defined in the standard DIN 5033 or in the equivalent international standard CIE 1931. In the standardized chromaticity diagram, a color is determined by an x and a y coordinate. FIG. 1 shows a standardized chromaticity diagram. All colors visible to the human eye lie within a color triangle T. A so-called achromatic point U is determined by the coordinates x=0.33 and y=0.33. Colors in the region around the achromatic point U are generally perceived as white. The colors assumed by daylight during the course of a day lie on a so-called D line D.
In order to provide an illumination device which is capable of radiating light whose color can be set, for example the colors which lie on the D line, three light sources of different colors are required in the illumination device. The colors of the three light sources lie, for example, at the points B, G, R illustrated in FIG. 1. In this case, in the example, point B lies in the blue region of the standardized chromaticity diagram, point G in the green region and point R in the red region. By setting the brightness of the three light sources, the illumination device can radiate all the colors which lie within the triangle BGR which is formed by the three points B, G and R.
According to the prior art, a described illumination device requires a circuit arrangement which contains a power supply for each of the three light sources. At least four connection lines are required to connect the three light sources, in this case a common reference potential being provided for all three light sources.
Each of the three power supplies requires a setting apparatus for setting the brightness of the light sources. If the brightness of the light radiated by the illumination device is intended to be set, without the color of the light being substantially altered, the three setting apparatuses must be actuated at the same time or a fourth setting apparatus needs to be provided. This fourth setting apparatus must make it possible for the power output of all three power supplies to be set at the same time.
In the prior art, it has proved disadvantageous that considerable outlay is required to provide the above-described luminous colors, and that setting color and brightness easily is impossible without additional outlay.